Spell Points are balanced.
At 5th level, your druid will have the option of creating up to 13 1st-level spell slots, 5 3rd-level spell slots, or some combination between those two extremes. Compare this to a druid of the same level, who may cast 9 spells total, only two of which may be as high as 3rd-level. In this instance, the druid with spell points will have the advantage... though when the regular druid's spell slots are broken down into points, they'll have the same value as the number of points a spell point druid would have.
At higher levels, however, the situation alters.
You can use spell points to create one slot each level of 6th or higher. You can't create another slot of the same level until you finish a long rest.
This particular rule very slightly throttles the power curve of the druid (who would have similar spell slot restrictions until 19th level anyway). That's not much of a change, but it is worth noting.
So how do higher level druids with and without spell points compare?
10th level: A druid without spell points can cast up to 15 spells a day, up to 2 of them 5th level and the rest evenly distributed among the levels. A druid with spell points can cast up to 9 5th-level spells or 32 1st level spells. Again, point value is identical- the advantage lies in the spell point druid's ability to effectively convert his lower spell slots into more 5th level slots.
15th level: If you're running one of the official campaigns, such as Tyranny of Dragons or Princes of the Apocalypse, this is probably as high as you'll have to worry about. Without spell points, your druid can cast 18 spells- the same as 10th level, plus 1 slot each for 6th, 7th, and 8th-level spells. With spell points, the high end looks identical- one each of the upper three slots, and the same possible combinations as 10th level.
Why are spell points balanced?
Consider three different spellcasting schemes.
Your druid casts as many high-level spells as possible.
Your druid casts as many spells as he can.
Your druid casts spells haphazardly as he needs them.
In the first case, congratulations- you've turned your druid into a warlock without the invocations. You'll be able to cast more spells than a warlock as long as they take only one short rest per day; after that, the warlock is more effective.
In the second case, you will be able to cast a number of spells that dwarfs all others... none of which will be higher than 1st level. This may be handy for a utility caster, but those who wish to control the battlefield or deal damage will be woefully underpowered.
The third case, by what must surely be a strange coincidence, causes you to cast spells in roughly the same amount and power as those without spell points.
Spell points as a variant would indeed give your druid an advantage, but only in terms of flexibility... and in the long run, your druid will either accept some hefty drawbacks to use that flexibility effectively, or cast spells in a similar spread to your other casters. Either way, your druid can look forward to more bookkeeping to keep track of it all.